I was able to get as many as 5 galleons, also after you collect all your money and refresh the page you will notice that the ‘motion’ of the Knight bus disappears. That’s how you know you’ve got everything you can from that moment.

when you zoom in the 2nd seen and the bus starts to move check out the stair way in the back a Galleon will fall from it but you have to grab it fast, you may need to refresh if you miss it, also the newspaper haning on the bed rail.

There are one or two galleons to collect if you double click. It’ll fall from the second floor when the bus begins to move, then slide first to one side (over the fallen umbrella and walking stick), then to the right.